Microbial rhodopsins, a diverse group of photoactive proteins found in Archaea, Bacteria, and Eukarya, function in photosensing and photoenergy harvesting and may have been present in the resource-limited early global environment. Four different physiological functions have been identified and characterized for nearly 5,000 retinal-binding photoreceptors,… (More)

Membrane proteins are key targets for pharmacological intervention because of their vital functions. Structural and functional studies of membrane proteins have been severely hampered because of the difficulties in producing sufficient quantities of properly folded and biologically active proteins. Here we generate a high-level expression system of integral… (More)

Haloarcula marismortui has been described to be nonmotile prior to the recent identification of flagellar filaments, suggesting the motile nature of H. marismortui. Here we observed the locomotion of freshly cultured H. marismortui cells and tracked the swimming trajectories via ImageJ. Trajectories of H. marismortui are intrinsically noisy, posing… (More)

The light-driven outward proton transporter assists energy production via an ATP synthase system best exemplified by the bacteriorhodopsin (BR) from Halobacterium salinarum, HsBR. As the only archaea able to survive in the resource-limited ecosystem of the Dead Sea, Haloarcula marismortui has been reported to have a unique dual-BR system, consisting of… (More)

Recently, a dual-bacteriorhodopsin system, containing HmbRI and HmbRII, has been found in Haloarcula marismortui (Mol. Microbiol. 2013, 88, 551-561), and the light-driven proton pump activities were intrinsically different in a wide pH range. Compared with bacteriorhodopsin in H. salinarum (HsbR), the identical steady-state absorption contours of HsbR and… (More)

Retinal bound light-driven proton pumps are widespread in eukaryotic and prokaryotic organisms. Among these pumps, bacteriorhodopsin (BR) proteins cooperate with ATP synthase to convert captured solar energy into a biologically consumable form, ATP. In an acidic environment or when pumped-out protons accumulate in the extracellular region, the maximum… (More)

Light is an important environmental signal for all organisms on earth because it is essential for physiological signalling and the regulation of most biological systems. Halophiles found in salt-saturated ponds encode various archaeal rhodopsins and thereby harvest various wavelengths of light either for ion transportation or as sensory mediators. HR… (More)

Microbial sensory rhodopsins are known to mediate phototaxis, and all of the known sensory rhodopsins execute this function with a specific cognate transducer that has two-transmembrane (2-TM) regions. In the genome of Haloarcula marismortui, a total of six rhodopsin genes were annotated, and we previously showed three of them to be the ion type and… (More)